Add preliminary support for exe packaging type (#908)

This is to allow fetching prebuilt binaries (such as
[protoc](https://repo1.maven.org/maven2/com/google/protobuf/protoc/)) in
the same way as other artifacts served by maven repositories.

Background: particularly useful for defining (lang) proto toolchains,
without having to compile nor manually maintain repository mappings
(checksums, etc.) for all supported platforms.

WORKSPACE

@@ -253,6 +253,10 @@ maven_install(
             group = "com.google.apis",
             version = "v1-rev235-1.25.0",
         ),
+        # https://github.com/bazelbuild/rules_jvm_external/issues/907
+        # Any two platforms to ensure that it doesn't work _only_ under the host operating system
+        "com.google.protobuf:protoc:exe:linux-x86_64:3.21.12",
+        "com.google.protobuf:protoc:exe:osx-aarch_64:3.21.12",
     ],
     generate_compat_repositories = True,
     maven_install_json = "//tests/custom_maven_install:regression_testing_install.json",

coursier.bzl

@@ -666,8 +666,11 @@ def make_coursier_dep_tree(
     cmd.extend(artifact_coordinates)
     if version_conflict_policy == "pinned":
         for coord in artifact_coordinates:
-            # Undo any `,classifier=` suffix from `utils.artifact_coordinate`.
-            cmd.extend(["--force-version", coord.split(",classifier=")[0]])
+            # Undo any `,classifier=` and/or `,type=` suffix from `utils.artifact_coordinate`.
+            cmd.extend([
+                "--force-version",
+                ",".join([c for c in coord.split(",") if not c.startswith("classifier=") and not c.startswith("type=")]),
+            ])
     cmd.extend(["--artifact-type", ",".join(SUPPORTED_PACKAGING_TYPES + ["src", "doc"])])
     cmd.append("--verbose" if _is_verbose(repository_ctx) else "--quiet")
     cmd.append("--no-default")

private/coursier_utilities.bzl

@@ -23,6 +23,7 @@ SUPPORTED_PACKAGING_TYPES = [
     "aar",
     "bundle",
     "eclipse-plugin",
+    "exe",
     "orbit",
     "test-jar",
     "hk2-jar",

private/dependency_tree_parser.bzl

@@ -36,15 +36,20 @@ def _genrule_copy_artifact_from_http_file(artifact, visibilities):
     if not len(artifact["urls"]):
         return ""
     http_file_repository = escape(artifact["coordinates"])
-    return "\n".join([
+    genrule = [
         "genrule(",
         "     name = \"%s_extension\"," % http_file_repository,
         "     srcs = [\"@%s//file\"]," % http_file_repository,
         "     outs = [\"%s\"]," % artifact["file"],
         "     cmd = \"cp $< $@\",",
+    ]
+    if get_packaging(artifact["coordinates"]) == "exe":
+        genrule.append("     executable = True,")
+    genrule.extend([
         "     visibility = [%s]" % (",".join(["\"%s\"" % v for v in visibilities])),
         ")",
     ])
+    return "\n".join(genrule)
 
 def _deduplicate_list(items):
     seen_items = {}
@@ -110,6 +115,7 @@ def _generate_imports(repository_ctx, dependencies, explicit_artifacts, neverlin
     # Iterate through the list of artifacts, and generate the target declaration strings.
     for artifact in dependencies:
         artifact_path = artifact["file"]
+
         # Skip the maven local dependencies if requested
         if skip_maven_local_dependencies and is_maven_local_path(artifact_path):
             continue
@@ -128,7 +134,7 @@ def _generate_imports(repository_ctx, dependencies, explicit_artifacts, neverlin
             all_imports.append(
                 "filegroup(\n\tname = \"%s\",\n\tsrcs = [\"%s\"],\n\ttags = [\"javadoc\"],\n)" % (target_label, artifact_path),
             )
-        elif get_packaging(artifact["coordinates"]) == "json":
+        elif get_packaging(artifact["coordinates"]) in ("exe", "json"):
             seen_imports[target_label] = True
             versioned_target_alias_label = "%s_extension" % escape(artifact["coordinates"])
             all_imports.append(

specs.bzl

@@ -251,13 +251,15 @@ json = struct(
 #
 
 #
-# Couriser expects artifacts to be defined in the form `group:artifact:version`, but it also supports two attributes: classifier and url.
+# Coursier expects artifacts to be defined in the form `group:artifact:version`, but it also supports some attributes:
+# `url`, `ext`, `classifier`, `exclude` and `type`.
 # In contrast with group, artifact and version, the attributes are a key=value comma-separated string appended at the end,
 # For example: `coursier fetch group:artifact:version,classifier=xxx,url=yyy`
 #
 def _artifact_to_coord(artifact):
     classifier = (",classifier=" + artifact["classifier"]) if artifact.get("classifier") != None else ""
-    return artifact["group"] + ":" + artifact["artifact"] + ":" + artifact["version"] + classifier
+    type = (",type=" + artifact["packaging"]) if artifact.get("packaging") != None else ""
+    return artifact["group"] + ":" + artifact["artifact"] + ":" + artifact["version"] + classifier + type
 
 #
 # Returns a string "{hostname} {user}:{password}" for a repository_spec

tests/custom_maven_install/regression_testing_install.json

@@ -1,7 +1,7 @@
 {
   "__AUTOGENERATED_FILE_DO_NOT_MODIFY_THIS_FILE_MANUALLY": "THERE_IS_NO_DATA_ONLY_ZUUL",
-  "__INPUT_ARTIFACTS_HASH": 187641354,
-  "__RESOLVED_ARTIFACTS_HASH": -835404132,
+  "__INPUT_ARTIFACTS_HASH": 1163673577,
+  "__RESOLVED_ARTIFACTS_HASH": 1891065348,
   "artifacts": {
     "android.arch.core:common": {
       "shasums": {
@@ -519,6 +519,13 @@
       },
       "version": "3.7.0"
     },
+    "com.google.protobuf:protoc:exe": {
+      "shasums": {
+        "linux-x86_64": "e6a75cf6660945fbfec0d321808442ce3649cd7820079eece1098c881b315f55",
+        "osx-aarch_64": "9f40368c858666e7036df0b9b58a4acd085fed58ab531294c3e5b5820f8af360"
+      },
+      "version": "3.21.12"
+    },
     "com.googlecode.matrix-toolkits-java:mtj": {
       "shasums": {
         "jar": "27a53db335bc6af524b30f97ec3fb4b6df65e7648d70e752447c7dd9bc4697c8"
@@ -5601,6 +5608,8 @@
       "com.google.j2objc:j2objc-annotations",
       "com.google.oauth-client:google-oauth-client",
       "com.google.protobuf:protobuf-java",
+      "com.google.protobuf:protoc:exe:linux-x86_64",
+      "com.google.protobuf:protoc:exe:osx-aarch_64",
       "com.googlecode.matrix-toolkits-java:mtj",
       "com.googlecode.netlib-java:netlib-java",
       "com.intellij:annotations",
@@ -5852,6 +5861,8 @@
       "com.google.j2objc:j2objc-annotations",
       "com.google.oauth-client:google-oauth-client",
       "com.google.protobuf:protobuf-java",
+      "com.google.protobuf:protoc:exe:linux-x86_64",
+      "com.google.protobuf:protoc:exe:osx-aarch_64",
       "com.googlecode.matrix-toolkits-java:mtj",
       "com.googlecode.netlib-java:netlib-java",
       "com.intellij:annotations",
@@ -6103,6 +6114,8 @@
       "com.google.j2objc:j2objc-annotations",
       "com.google.oauth-client:google-oauth-client",
       "com.google.protobuf:protobuf-java",
+      "com.google.protobuf:protoc:exe:linux-x86_64",
+      "com.google.protobuf:protoc:exe:osx-aarch_64",
       "com.googlecode.matrix-toolkits-java:mtj",
       "com.googlecode.netlib-java:netlib-java",
       "com.intellij:annotations",

tests/unit/build_tests/BUILD

@@ -1,4 +1,5 @@
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load("@bazel_skylib//rules:native_binary.bzl", "native_binary")
 
 # Regression tests for particular artifacts that revealed problems for this
 # project.
@@ -19,6 +20,23 @@ build_test(
         "@regression_testing//:com_fasterxml_jackson_jackson_bom",
         "@regression_testing//:org_junit_junit_bom",
         "@regression_testing//:io_netty_netty_tcnative_boringssl_static",
+        "@regression_testing//:com_google_protobuf_protoc_linux_x86_64",
+        "@regression_testing//:com_google_protobuf_protoc_osx_aarch_64",
+    ],
+)
+
+# Note: skylib's `native_test` would fail on "Exec format error" under the other platform, hence the following 2 steps
+[native_binary(
+    name = "src_that_refers_to_a_valid_executable_{}_target".format(platform),
+    src = "@regression_testing//:com_google_protobuf_protoc_{}".format(platform),
+    out = "protoc_{}.exe".format(platform),
+) for platform in ("linux_x86_64", "osx_aarch_64")]
+
+build_test(
+    name = "native_binaries_indeed_refer_to_valid_executable_targets",
+    targets = [
+        "src_that_refers_to_a_valid_executable_{}_target".format(platform)
+        for platform in ("linux_x86_64", "osx_aarch_64")
     ],
 )